516 



REPORT OF THE COMMISSIONER OF FISHERIES. 



as compared with those taken in the deeper water, the hitter using 

 plankton for food much oftener and in greater quantities than the 

 former, A distinct difference was also found in the food of the perch 

 living" near the shore and those caught during the winter through the 

 ice. These latter were taken well out in the lake, and were so differ- 

 ent from the others in food contents and scarcity of parasites that 

 the}^ are entitled to special mention. 



The scarcitj^ of literature on the food of fresh-water fishes is very 

 noticeable, and we could find but little information on the subject. 

 When one considers the amount of work that is being done by the 

 federal and state fish commissions in stocking our inland waters, it 

 is surprising to find that so few observations have been made and 

 recorded concerning any of the important economic questions bearing 

 on this subject. 



In classifying our fishes we have followed Jordan and Evermann. 



1. Lejpisosteus osseus, gar pike. 



A single specimen of this fish was obtained in October from Lake 

 Mendota. No food was found in the alimentary tract. Two cestodes 

 and a few small trematodes were present, none of which has yet been 

 identified. 



2, Am la calva., dog-fish. 



Thirteen specimens of dog-fish were examined, 4 of which were 

 without any food; 7 of the 9 in which food was found contained craw- 

 fish, the other 2, minnows. 



Parasites were very prevalent, ever}'^ fish having them in considera- 

 ble numbers. The following table gives the kinds of parasites found, 

 the parts of the host in which they occurred, and the number of fish 

 in which each kind of parasite was found: 



The trematodes were all Azygia tereticolle^ which fluke was also 

 present on the gills of 2 fishes. One fish had an enc^^sted cestode in 

 the spleen. 



The prevalence of cestodes was noticeable, they being found in every 

 fish examined and in great abundance, 100 to 300 occurring in many 

 of the fish. There were at least 2 species of cestodes and 2 species of 

 Acanthocephala present. The frequent occurrence of cestodes in the 

 stomach was due to the fact that many which were found in the intes- 

 tine were fastened to the wall of the stomach, stretching from there 



